with open('Desktop\\poem.txt','w',encoding='utf-8') as f:
    f.write('我欲乘风归去，\n')
    f.write('又恐琼楼玉宇，\n')
    f.write('高处不胜寒。\n')
with open('Desktop\\poem.txt','a',encoding='utf-8') as f:
    f.write('起舞弄清影，\n')
    f.write('何似在人间。\n')# OK OK
    